Yin Laiyin, Schrank Franziska, Gross-Weege Nicolas, Schug David, Schulz Volkmar
Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany.
Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany.
Phys Med Biol. 2021 Apr 28;66(9). doi: 10.1088/1361-6560/abf606.
Integration of magnetic resonance imaging (MRI) and positron emission tomography (PET) into a simultaneous device calls for adaptations of the radio frequency (RF) shielding concept. Conventional PET module housings fully encase the entire PET detector to reduce mutual interference. Excluding passive components, i.e. scintillators, from the housings, offers integration advantages, e.g. by reducing the overall housing volume or utilizing bigger scintillators. However, locating the scintillator outside of the RF shielding requires an optically transparent RF shielding interface between the scintillators and the photodetector to close the aperture. Therefore, a careful evaluation and selection of RF materials is essential to ensure an excellent PET/MRI system performance. To this end, we examined 10 materials (coated glasses, coated foils, meshes). The shielding effectiveness (SE) was evaluated at 100 and 300 MHz. PET performance was tested for single event registration and coincident events by integrating the material into the PET detector stack between the digital silicon photomultiplier photodetector array and one-to-one coupled scintillator. We determined photon attenuation (PA), energy resolution (dE/E), and coincidence resolving time (CRT) and compared to reference measurements for each material group. MRI compatibility was assessed by analyzing the material influence on the main magnetic field (B) homogeneity. The coated glasses and foils exhibited SEs of up to 25 dB at 300 MHz. Both had a PA < 23% with dE/E and CRT comparable to the reference measurements, and no measurable impact on the Bfield was registered. The meshes exhibited higher SEs up to 56 dB, but also a PA > 58% with a higher impact on dE/E and CRT. Only one mesh affected Bhomogeneity. Overall, we recommend the coated foil HS 9400 for integration concepts as it exhibited a good performance with SE = 25 dB, PA = 22%, resulting in a PET performance of dE/E = 12% and CRT = 274 ps.
将磁共振成像（MRI）和正电子发射断层扫描（PET）集成到一个同步设备中，需要对射频（RF）屏蔽概念进行调整。传统的PET模块外壳完全包裹整个PET探测器，以减少相互干扰。将无源部件（即闪烁体）排除在外壳之外具有集成优势，例如通过减小整体外壳体积或使用更大的闪烁体。然而，将闪烁体放置在RF屏蔽之外需要在闪烁体和光电探测器之间有一个光学透明的RF屏蔽接口来封闭孔径。因此，仔细评估和选择RF材料对于确保优异的PET/MRI系统性能至关重要。为此，我们研究了10种材料（镀膜玻璃、镀膜箔、网）。在100和300 MHz下评估屏蔽效能（SE）。通过将材料集成到数字硅光电倍增管光电探测器阵列和一对一耦合闪烁体之间的PET探测器堆栈中，测试PET对单事件记录和符合事件的性能。我们确定了光子衰减（PA）、能量分辨率（dE/E）和符合分辨时间（CRT），并与每个材料组的参考测量值进行比较。通过分析材料对主磁场（B）均匀性的影响来评估MRI兼容性。镀膜玻璃和镀膜箔在300 MHz时表现出高达25 dB的SE。两者的PA均<23%，dE/E和CRT与参考测量值相当，并且未记录到对磁场的可测量影响。网表现出高达56 dB的更高SE，但PA也大于58%，对dE/E和CRT有更大影响。只有一种网影响B均匀性。总体而言，我们推荐镀膜箔HS 9400用于集成概念，因为它表现出良好的性能，SE = 25 dB，PA = 22%，导致PET性能为dE/E = 12%，CRT = 274 ps。
